String tensioning mechanism

ABSTRACT

The invention relates to racket stringing apparatus including novel means for tensioning the strings thereof during stringing of a racket frame and determining the degree of tension applied.

United States Patent [191 Miyagawa et a1.

STRING TENSIONING MECHANISM Inventors: Frank H. Miyagawa; Daniel D.

Kipnis, both of Chicago; Thomas C. Mills, Bartlett, all of 111.

Assigneez. Tremont Research Co., Inc.,

Chicago, 111.

Filed: Jan. 15, 1973 Appl. No.: 323,900

U.S. Cl. 73/145, 73/95 Int. Cl. G011 5/06 Field of Search 73/143, 145, 141 AB, 95

References Cited UNlTED STATES PATENTS Roberts et a1. 73/145 1 July 16, 1974 11/1937 Doll 273/73 A X 3,441,275 4/1969 Held 73/145 3,511,502 5/1970 .Spenle 273/73 A 3,635,080 1/1972 Krueger et a1. 73/145 Primary Examiner-Charles A. Ruehl Attorney, Agent, or Firm-Samue1 W. Kipnis [57] ABSTRACT The invention relates to racket stringing apparatus ineluding novel means for tensioning the strings thereof during stringing of a racket frame and determining the degree of tension applied.

10 Claims, 8 Drawing Figures PATENTED JUL 1 6 I974 sum 1 nr 3 PATENTED JUL 1 61974 W I I IMMW/ STRING TENSIONING MECHANISM The invention relates to apparatus used for the stringing of tennis rackets and the like.

Known stringing apparatus generally requires a turntable upon which the racket frame to be strung is clamped, which turntable is locked during successive passes of the string through holes in the racket frame. The string is pulled taut by power actuated or foot actuated mechanisms and clamp means is provided to retain a taut string taut during the threading and tensioning of a successive string. In such known machines the inclusion of power or foot actuated string tensioning mechanism is costly to manufacture and is income nient and cumbersome to use and further denies portability of the apparatus and in most instances lacks an accurate tension guage.

The present invention is concerned generally with the provision of novel clamp means to hold the racket frame and novel clamp elements to secure the string tensioned during the threading of successive string portions and particularly to the novel construction and location of manually controlled easily readable torque means to tension the strings to a predetermined degree of tension.

It is therefore an object of the invention to provide novel apparatus for stringing tennis rackets and the like.

Another object is to provide novel clamp means for securing the racket frame to the apparatus.

Another object is to.provide novel means for securing a tensioned string portion during threading and tensioning of successive string portions.

Another object is to provide novel string tensioning means and an associated torque gauge for determining the degree of tension applied to the string.

Another object is to provide novel means to moun the apparatus on a support surface.

Another object is to provide apparatus of the character referred to which is not expensive or difficult to manufacture and which is simple to use and very efficient in its use.

Other objects and advantages of the invention will become apparent with reference to the following description and accompanying drawings. In the drawings:

FIG. I is a plan view of the string threading and tensioning apparatus showing a partially strung racket frame mounted thereon.

FIG. 2 is a side elevational view of the apparatus, showing the racket frame in section.

FIG. 3 is a vertical sectional view showing the pivotal mounting for the adjustable elements, taken substantially along line 3--3 of FIG. 1.

FIG. 4 is an enlarged longitudinal sectional view of the tensioning mechanism taken substantially on line 4-4 of FIG. 1.

FIG. 5 is a side elevational view of the tensioning mechanism showing the guide rollers thereon as viewed along line 5--5 of FIG. 6.

FIG. 6 is a vertical transverse sectional view of the tensioning arm as viewed along line 6-6 of FIG. 4.

FIG. 7 is a horizontal sectional view of the tensioning mechanism taken along line 7-7 of FIG. 4.

FIG. 8 is a detailed sectional view of the swivel clamp aw.

Referring to the exemplary embodiment of the invention as disclosed in the accompanying drawings, the apparatus includes a base l1, a turntable 12 which is rotatably mounted on the base and which includes a pair of racket frame supports 13 having associated with said supports clamping plates 14 used to secure the racket frame 35 firmly to the turntable. The base 11 may be removably secured to work surface 15 by means of corner bolts 16 and clamps 17. The base includes a longitudinally extending arm 18 having mounted adjacent to its free extended end a string tensioning mechanism generally indicated at 19.

Arranged above the turntable 12 and rotatable relative thereto on a common axis, is an arm 21 carrying a string clamping bracket 22. This bracket is best shown in FIG. 8 and it comprises a mounting pin 22a removably seated in the arm 21 and fixedly mounting a clamp element 22b. The upper end of pin 22a is bent horizontally to receive a movable clamp element 22c and screw means 22d is threaded on said pin to secure the clamp.

The pivotal mounting for the turntable 12 and clamp arm 21 is best illustrated in FIG. 3. A there shown the base 11 has a relatively large aperture defined by circular flange 23 in which is seated a flanged collar 24 having an upstanding axial boss 25 apertured to receive a bolt 26. The flanged collar 24 is secured in place by a washer 27 that is secured thereto by screws 28.

Nested over boss 25 is a socket 29 formed integral with turntable l2. Seated on top of the turntable is an antifriction washer 31. The arm 21 has an axial elongated aperture 32, and an elongated washer 33 is seated thereon. The assembly is secured together by a washer-nut assembly 34 screwed onto the upper threaded end of'bolt 26. It is evident, upon viewing FIGS. 1 and 3, that the clamp arm 21 may be adjusted longitudinally and rotatably relative to the turntable 12 upon lossening and then tightening of the nut 34, all for a purpose to be explained presently.

Insofar as the structure has been described, its use is substantially as follows. A racket frame 35 is secured to the turntable 12 between the supports 13 and their related clamps 14 in a manner best shown in FIG. 1. To string the racket frame, a string is initially threaded through two opposed holes in the racket frame, as indicated at 36a, and a clamp 37, carried by the turntable 12 is secured firmly about said string 36a at a point closely adjacent to the racket frame 35. The string then is reversed, carrying it back through the next adjacent pair of holes in the racket frame, as shown at 36b. and the free end portion thereof is clamped in a clamp 38 carried by the tensioning mechanism 19. Tension is then applied, in a manner to be described presently, on the clamped string 36b so as to draw it taut. While the string 36b is still held taut by the clamp 37, the clamp 22 on the clamp arm 21 is moved into position shown in FIG. 1 and clamped tightly about the taut string 36b. The tension clamp 38 may now be released.

The turntable l2 and clamp arm 21 with the partially strung racket frame still secured to the turntable are rotated about so as to permit a third string section to be strung in the racket frame. This newly strung string is, in the manner previously explained, clamped in the tensioning mechanism clamp 38 and tensioned. The clamp 22 on clamp arm 21 is then released and the clamp arm swung approximately 180 into the full line position shown in FIG. 1 where it is then clamped to the third string section followed by release of the tensioning mechanism clamp 38. The sequence of stringing is repeated until the racket frame is completely strung.

The tensioning mechanism 19 is best illustrated in FIGS. 1 and 4 to 7. As best shown in FIGS. 1 and 4, the arm extension 18 on the base 11 comprises a hollow elongated frame having a longitudinal slot 39 in which the tensioning mechanism 19 is mounted for longitudinal movement. Specifically, the tensioning mechanism includes a cover plate 41 that overlies the slot 39 and which has depending through the slot and into the arm 18, a boss 42 having on its side walls pairs of rollers 43 that are engaged with and ride along longitudinal rails 44 provided within the arm. The boss has a longitudinal aperture 45 therethrough adapted to receive a tensioning screw 46 freely therethrough. This screw projects freely out of the end wall 18a (FIG. 4) of base arm 18 and carries a hand crank 47 on its projecting end.

The forwardly extending end of screw 46 is threaded through a slide block 48 and has its end rotatably anchored in a boss 49 depending from the top wall of the base arm 18. As best shown in FIG. 4, a pair of guide rods 50, secured firmly in the slide block 48, project freely through boss 42 so as to prevent rotation of the slide block 48 when screw 46 is rotated. As described, when a string is clamped at 38 to the tensioning mechanism and the screw 46 is rotated to draw the mechanism in a direction to make the string taut, the entire mechanism is advanced toward the end wall 46. This will initially tension the string but will not render it as critically taut as it must be.

It is essential however that each string section be drawn taut to a predetermined degree of tension. This is accomplished by providing the tensioning mechanism with a visible gauge having pound torque readings thereon. Accordingly, as soon as the string is initially tensioned, continued rotation of the screw 46 will draw the slide block 48 towards the boss 42 and against the action of a compression spring 51. When this occurs, the lead end of a longitudinally projecting finger 52 (FIGS. 4, 7) on said slide block will engage a stud 53 depending from a quadrant-like plate 54 pivotally mounted at 55 to the underside of the cover plate 41 so as to cause said plate 54 to rotate about its axis 55. The plate 54 has on its top surface a series of graduated numerals representative of pounds tension, which are selectively visible through a window opening 56 in cover plate 41. The scale of numbering preferably runs from 45 to 70, each representative of pounds tension applied to the string. Present practice is to tension the string at about 55 pounds in which instance the screw 46 is rotated until the slide block 48 has advanced a sufficient distance to locate the numeral 55 beneath the window opening. During this tension adjustment, the rollers 43 on boss 42, being guided on rails 44, will prevent canting or binding.

Although I have described. a preferred embodiment of my invention, in considerable detail, it will be understood that the description thereof is intended to be illustrative, rather than restrictive, as details of the structure may be modified or changed without departing from the spirit or scope of the invention. Accordingly, I do not desire to be restricted to the exact construction shown and described.

I claim:

1. String tensioning mechanism comprising a hollow elongated frame having a longitudinal slot in its top wall, a plate overlying said slot and to which a string to be tensioned is attached, a guide boss integral with said plate and projecting through the slot, an operating screw in said frame extending freely through said boss, a slide block threaded on said screw, a compression spring between the bossand slide block, a window opening in the plate, a calibrated dial carried by the plate and movable relative thereto to carry its calibrations into register with the window opening, and means on the slide block engageable with the calibrated dial to move said dial when the slide block is drawn toward the boss while tensioning a string.

2. The mechanism recited in claim 1, wherein the plate-carries clamp means to secure the string thereto.

3. The mechanism recited in claim I, wherein the calibrated dial has a projection engageable by the means on the slide block to move said dial.

4. The mechanism recited in claim 3, wherein the means on the slide block comprises a rigid extension.

5. The mechanism recited in claim 1, wherein the dial block and slideable in the boss.

frame has guides thereon and the boss has rollers bearing on the guides.

10. The mechanism recited in claim I, wherein the compression spring surrounds the screw. 

1. String tensioning mechanism comprising a hollow elongated frame having a longitudinal slot in its top wall, a plate overlying said slot and to which a string to be tensioned is attached, a guide boss integral with said plate and projecting through the slot, an operating screw in said frame extending freely through said boss, a slide block threaded on said screw, a compression spring between the boss and slide block, a window opening in the plate, a calibrated dial carried by the plate and movable relative thereto to carry its calibrations into register with the window opening, and means on the slide block engageable with the calibrated dial to move said dial when the slide block is drawn toward the boss while tensioning a string.
 2. The mechanism recited in claim 1, wherein the plate carries clamp means to secure the string thereto.
 3. The mechanism recited in claim 1, wherein the calibrated dial has a projection engageable by the means on the slide block to move said dial.
 4. The mechanism recited in claim 3, wherein the means on the slide block comprises a rigid extension.
 5. The mechanisM recited in claim 1, wherein the dial is located on the underside of the plate.
 6. The mechanism recited in claim 1, wherein guide means is provided to prevent rotation of the slide block.
 7. The mechanism recited in claim 6, wherein the guide means comprises rods firmly secured in the slide block and slideable in the boss.
 8. The mechanism recited in claim 1, wherein the guide means limits movement of the slide block away from the boss.
 9. The mechanism recited in claim 1, wherein the frame has guides thereon and the boss has rollers bearing on the guides.
 10. The mechanism recited in claim 1, wherein the compression spring surrounds the screw. 